Nuclear medical imaging such as single-photon emission computed tomography (SPECT) and positron emission computed tomography (PET) have become important tools in pre-clinical and clinical imaging applications. A major task in developing a nuclear medical imaging camera is the electronics system. The problem is that such electronics requires a significant development effort beyond the capability of most research groups. While commercial PET and SPECT camera manufacturers have developed such electronics, they are typically optimized for specific products (and so are difficult to adapt and usually are proprietary (and so are not available to most researchers). Currently, research groups with sufficient resources are forced to independently develop their own customized electronics for specific projects. Research groups without sufficient resources or expertise are forced instead to depend on commercially available electronics with limited flexibility for handling high-performance detectors and limited access to source code for modification. Overall, this situation can lead to detector and camera design compromises that sacrifice performance, due to the difficulties of designing the electronics system. It also wastes the limited resources (funding, time, expertise, etc.) since researchers are working independently and duplicating efforts. In this project we propose to develop a flexible, scalable, and high-performance OpenPET electronics system with open availability to overcome these problems. While there are a tremendous number of variations, the relatively simple nature of the data ultimately collected implies that there can be a common set of requirements, which would allow us to develop OpenPET into a community resource that would resolve one of the major problems faced by developers of nuclear medical imaging cameras. Each gamma ray interaction is characterized by a small number of attributes, usually no more than a three-dimensional interaction position, a measure of the deposited energy, and an interaction time. Data are collected either as single interactions or coincident pairs, and only a small amount of ancillary information is needed (such as count rates, the position of an attenuation source, or a gating signal). The OpenPET design is largely driven by the need for flexibility, high performance and open- source. We will achieve these needs by: (1) extensive use of field-programmable gate arrays (FPGAs) to provide highly programmable electronics, (2) utilizing waveform sampling in the electronics to make the signal processing more flexible and to achieve higher performance than conventional analog electronics circuitry, (3) having ready procurement of the system hardware from pre-arranged vendors, (4) having documentation and source code freely available, and (5) developing a user community that will pool their software and hardware enhancements. The ultimate goal is to provide a rich set of solution and enabling technology for the research community at large.